In an expanding plug of this type known from German published patent application 31 45 319 the expanding cone consists of zinc die casting. Such expanding cones of die casting are comparatively heavy and having a correspondingly high material need. Technically these expanding cones are satisfying and have, therefore, been generally accepted in practice.
Of course the expanding cones are known to be made of plastics material without any substantial change in shape; but these cones have not been generally accepted, since the shear strength of the internal thread for the expanding screw is not sufficiently high.
A plug is already known from German published patent application 27 11 845 which consists of several external clamping jaws, in which a plug nucleus provided with projections is arranged to expand these clamping jaws. Without being specific this prior publication explains that this plug nucleus, too, might consist of a cylindrically rolled sheet with correspondingly punched-out recesses. Further hints cannot be taken from this publication.